# compressibility of NatGas at high pressure
**URL:** https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644
**Category:** Factual Questions
**Created:** [June 10, 2010, 1:40pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644 "2010-06-10T13:40:35Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@bri1600bv](https://boards.straightdope.com/u/bri1600bv)
#### Post date: [June 10, 2010, 1:40pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644/1 "2010-06-10T13:40:35Z")
Yesterday BP said it pulled up 600,000 gallons of oil, rougly 100,000 cubic feet (I believe) and 30 MILLION cubic feet of gas. Or about 99.7% by volume natural gas.
But at the BOP, at the bottom of the ocean, 5000 feet down, at 2200 psi pressure, what is the volume of natural gas, ie how much is it compressed? IE coming out of the BOP is it 90% gas, 80% gas? How much volume would 30M cft of gas be at 2200 psi?
Pv=nRT is all I know from high school, but I"m a little rusty.
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### Author:  [@nolonger\_lurking](https://boards.straightdope.com/u/nolonger_lurking)
#### Post date: [June 10, 2010, 2:29pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644/2 "2010-06-10T14:29:36Z")
Keep in mind that temperature is very important, and I don’t know that well’s gas composition.
Using a mixture of mostly methane, with smaller amounts of ethane, CO2, pentanes, propanes, and butanes, I get the following properties.
```auto
Temperature Pressure Density
(°F) (psia) (lbm/ft³)
60.000 14.700 0.056249
0.00000 2200.0 17.828
100.00 2200.0 10.794
200.00 2200.0 7.6617
300.00 2200.0 6.1147
```
The bottom of the ocean is pretty cold, but the well could be significantly warmer. Either way, it is between 100 and 300 Standard Cubic Feet for each Actual cubic foot.
Using your numbers, I get 80208 cubic feet of oil and 100000 to 300000 cubic feet of gas, but I’m not sure I buy it. I can find densities pretty accurately if someone has temps, pressures, and a good composition.
btw, PV=nRT gives something an SCF to ACF ratio of 150 at constant temp, so without more info I haven’t really helped you.
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### Author:  [@bri1600bv](https://boards.straightdope.com/u/bri1600bv)
#### Post date: [June 10, 2010, 2:34pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644/3 "2010-06-10T14:34:05Z")
Wow thanks.
I think it comes up about 300 degrees F or som but it probably cools quickly in water.
So it reduces by a factor of 100 or so.
So 3/4 gas instead of 99.7%, big difference.
I was hoping most of that “plume” they show was gas but it looks like only 3/4 or so is.
thanks for your help.
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### Author:  [@hibernicus](https://boards.straightdope.com/u/hibernicus)
#### Post date: [June 10, 2010, 10:57pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644/4 "2010-06-10T22:57:08Z")
> [@bri1600bv](#):
>
> Yesterday BP said it pulled up 600,000 gallons of oil, rougly 100,000 cubic feet (I believe) and 30 MILLION cubic feet of gas. Or about 99.7% by volume natural gas.
>
> But at the BOP, at the bottom of the ocean, 5000 feet down, at 2200 psi pressure, what is the volume of natural gas, ie how much is it compressed? IE coming out of the BOP is it 90% gas, 80% gas? How much volume would 30M cft of gas be at 2200 psi?
>
> Pv=nRT is all I know from high school, but I"m a little rusty.
Pv=RT is an ideal gas equation, and doesn’t work at high pressures. You have to multiply by the supercompressibility Z (Z=Pv/RT). 2200 psi is about 150 bar, and depending on temperature Z could be maybe 0.75. So you’ve got 30 million/150 \* 0.75 = 150,000 cubic feet. Approximately.
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### Author:  [@spingears](https://boards.straightdope.com/u/spingears)
#### Post date: [June 12, 2010, 8:10pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644/5 "2010-06-12T20:10:55Z")
At the high pressure and low temperature at 5,000 ft there is only liquid gas or possibly a crystaline form. Liquid or crystals would be pretty much non-compressible further.
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### Author:  [@hibernicus](https://boards.straightdope.com/u/hibernicus)
#### Post date: [June 12, 2010, 10:41pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644/6 "2010-06-12T22:41:40Z")
> [@spingears](#):
>
> At the high pressure and low temperature at 5,000 ft there is only liquid gas or possibly a crystaline form. Liquid or crystals would be pretty much non-compressible further.
The critical temperature of methane is 190.4K. Above this temperature, it is impossible to convert methane to liquid by the application of any amount of pressure. Methane at this temperature and pressure is a supercritical fluid and is compressible.
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### Author:  [@spingears](https://boards.straightdope.com/u/spingears)
#### Post date: [June 17, 2010, 1:41pm UTC](https://boards.straightdope.com/t/compressibility-of-natgas-at-high-pressure/542644/7 "2010-06-17T13:41:27Z")
hibernicus: “IT” is not natural gas or methane per se but hydrates or clathrates of methane per Google search for “Methane at 5,000 ft. ocean depth.”